Usually in heavy vehicles each track roller, or each pair of track roller "twins", is suspended using a torsion bar one end of which is anchored to one side of the hull and which passes through the body of the vehicle to the twin roller opposite. This type of long torsion bar has been developed to assimilate the large movements that each track roller is subjected to when crossing rough terrain.
The standard design has a number of disadvantages, particularly for combat vehicles. These disadvantages include:
the whole width of the vehicle must be utilized to obtain sufficient travel in the suspension, PA1 long torsion bars reduce the available space inside the vehicle, PA1 the vehicle must be made taller because the torsion bars have reduced the available interior space. In the case of large vehicles this can increase the weight by approximately 2 tons because the bars are fully protected by armour plating, PA1 tall vehicles present a larger target, PA1 the structure is fixed, i.e. it is not possible to raise or lower the vehicle in order to alter the ground clearance when driving cross country or to take up a high or low combat position, PA1 the track rollers on one side become longitudinally displaced in relation to the track rollers on the other side due to the length of the torsion rods and because they lie adjacent to each other.